Manchester United have made a long-term decision not to sign any players aged 26 or above for large transfer fees because of new financial stipulations that have been put in place at Old Trafford to shape the club's recruitment policy. Dimitar Berbatov, who was 27 when he signed from Tottenham Hotspur last September, has been described as the "last of his kind" in a move that has immediate implications for their attempts to replace Cristiano Ronaldo.

The restrictions automatically mean that Sir Alex Ferguson's admiration for Franck Ribéry will not manifest itself in a concerted attempt to sign the France international. Karl-Heinz Rummenigge, Bayern Munich's chairman, said yesterday that United, Chelsea and Barcelona had all lodged bids but the Premier League champions say that is not true.

Instead, the policy from now onwards is that the club will have a strict age-before-ability approach in which they will sign players in big-money deals only if they will retain a significant market value some years after signing a five- or six-year contract.

Karim Benzema, the Lyon striker, would fit into their strategy, being 21, but Ribéry is considered too old even though he turned 26 only two months ago and is approaching what are generally considered the best years of a footballer's career. United's thinking is that Ribéry would cost close to £60m and have no significant resale value, leaving Chelsea, who have tabled a formal bid believed to be around £40m, hopeful of signing the France international, particularly as Real Madrid's interest appears to have cooled.

The same policy applies to David Villa, the outstanding Valencia striker who is on the market at the age of 27 for a fee of around £45m, as well as the man who scored the first goal against United in the Champions League final, Barcelona's 28-year-old forward Samuel Eto'o. Both are ruled out unless there is a rethink at Old Trafford.

United are aware that the policy may not go down well with those supporters who are expecting high-profile replacements to fill the void left by Ronaldo's impending world-record transfer to Real Madrid. However, the club insists it makes sound business sense not to bring in a player for £30m or more who cannot be sold for another high valuation some years after signing his contract.

This explains why United did not make any effort to sign Kaka, the Brazil international and former world footballer of the year, when he became available for £59m from Milan, even though Ferguson has now admitted he knew for virtually all of last season that Ronaldo would be leaving this summer. Kaka was 27 in April and that does not fit into United's strategy of not buying expensive players whose values will then plummet.

Berbatov was considered an exception to the rule when he signed for £30.75m but Ferguson is now working under the knowledge that his chief executive, David Gill, and the club's American owners, the Glazer family, expect him to pursue younger players who could conceivably make the club a profit.

Ronaldo was 18 when he signed from Sporting Lisbon for £12.2m six years ago and United, despite being renowned for wanting to keep their better players, are placing a heavy emphasis on bringing in people who could feasibly make them money. The policy has been gradually evolving over recent years, with Nemanja Vidic, Patrice Evra, Michael Carrick, Anderson and Nani all 25 and below when they were signed.

United are now targeting Antonio Valencia, Wigan Athletic's 23-year-old Ecuador international, to take over from Ronaldo on the right side of their attack but face competition for the 23-year-old from Madrid and an unnamed club, believed to be Bayern Munich. "It all rests on where the lad wants to go to: Man United, Real Madrid or the other European club," said Wigan's chairman, Dave Whelan. "We can't force him where to go. We will have a meeting with United and Real Madrid in the next three or four days, see what offers are on the table and then present them to the lad and he will decide where he wants to go or if he wants to go. We would never stop a player from going to a top club. The lad comes back from holiday this weekend and I expect it will be another 10 to 14 days before a deal is done.

"Real Madrid have been in contact once a week for the last six weeks. I thought them agreeing a deal with Ronaldo would fulfil their requirements but it hasn't done, as they've been in touch again since then. There have been fees spoken about but have we had a bid put in black and white? No." Whelan added that he would not increase the asking price for Valencia in light of Ronaldo's £80m sale.

Ferguson is also still hoping to persuade Carlos Tevez to sign a permanent deal with the club, despite the Argentinian saying publicly and privately that he has no plans to return to Old Trafford when he becomes a free agent on 30 June. Tevez, also a target for Manchester City, Chelsea – who do not believe they will land him – and Liverpool, is 25 and United's initial reluctance to pay the £25.5m fee wanted by the investors who own his economic rights partly derived from a concern about what he might be worth to them towards the end of a five-year contract. Gill has already publicly stated that he thinks Tevez's valuation is a "bit toppy."